/*
 * Copyright (C) 2008 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.primitives;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkElementIndex;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkPositionIndexes;

import java.io.Serializable;
import java.util.AbstractList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.RandomAccess;

import com.google.common.annotations.GwtCompatible;

/**
 * Static utility methods pertaining to {@code float} primitives, that are not
 * already found in either {@link Float} or {@link Arrays}.
 * 
 * @author Kevin Bourrillion
 * @since 2009.09.15 <b>tentative</b>
 */
@GwtCompatible
public final class Floats {
    private Floats() {
    }

    /**
     * Returns a hash code for {@code value}; equal to the result of invoking
     * {@code ((Float) value).hashCode()}.
     * 
     * @param value
     *            a primitive {@code float} value
     * @return a hash code for the value
     */
    public static int hashCode(float value) {
        // TODO: is there a better way, that's still gwt-safe?
        return ((Float) value).hashCode();
    }

    /**
     * Compares the two specified {@code float} values using
     * {@link Float#compare(float, float)}. You may prefer to invoke that method
     * directly; this method exists only for consistency with the other
     * utilities in this package.
     * 
     * @param a
     *            the first {@code float} to compare
     * @param b
     *            the second {@code float} to compare
     * @return the result of invoking {@link Float#compare(float, float)}
     */
    public static int compare(float a, float b) {
        return Float.compare(a, b);
    }

    /**
     * Returns {@code true} if {@code target} is present as an element anywhere
     * in {@code array}. Note that this always returns {@code false} when
     * {@code target} is {@code NaN}.
     * 
     * @param array
     *            an array of {@code float} values, possibly empty
     * @param target
     *            a primitive {@code float} value
     * @return {@code true} if {@code array[i] == target} for some value of
     *         {@code i}
     */
    public static boolean contains(float[] array, float target) {
        for (float value : array) {
            if (value == target) {
                return true;
            }
        }
        return false;
    }

    /**
     * Returns the index of the first appearance of the value {@code target} in
     * {@code array}. Note that this always returns {@code -1} when
     * {@code target} is {@code NaN}.
     * 
     * @param array
     *            an array of {@code float} values, possibly empty
     * @param target
     *            a primitive {@code float} value
     * @return the least index {@code i} for which {@code array[i] == target},
     *         or {@code -1} if no such index exists.
     */
    public static int indexOf(float[] array, float target) {
        return indexOf(array, target, 0, array.length);
    }

    // TODO: consider making this public
    private static int indexOf(float[] array, float target, int start, int end) {
        for (int i = start; i < end; i++) {
            if (array[i] == target) {
                return i;
            }
        }
        return -1;
    }

    /**
     * Returns the start position of the first occurrence of the specified
     * {@code target} within {@code array}, or {@code -1} if there is no such
     * occurrence.
     * 
     * <p>
     * More formally, returns the lowest index {@code i} such that
     * {@code java.util.Arrays.copyOfRange(array, i, i + target.length)}
     * contains exactly the same elements as {@code target}.
     * 
     * <p>
     * Note that this always returns {@code -1} when {@code target} contains
     * {@code NaN}.
     * 
     * @param array
     *            the array to search for the sequence {@code target}
     * @param target
     *            the array to search for as a sub-sequence of {@code array}
     */
    public static int indexOf(float[] array, float[] target) {
        checkNotNull(array, "array");
        checkNotNull(target, "target");
        if (target.length == 0) {
            return 0;
        }

        outer: for (int i = 0; i < array.length - target.length + 1; i++) {
            for (int j = 0; j < target.length; j++) {
                if (array[i + j] != target[j]) {
                    continue outer;
                }
            }
            return i;
        }
        return -1;
    }

    /**
     * Returns the index of the last appearance of the value {@code target} in
     * {@code array}. Note that this always returns {@code -1} when
     * {@code target} is {@code NaN}.
     * 
     * @param array
     *            an array of {@code float} values, possibly empty
     * @param target
     *            a primitive {@code float} value
     * @return the greatest index {@code i} for which {@code array[i] == target}
     *         , or {@code -1} if no such index exists.
     */
    public static int lastIndexOf(float[] array, float target) {
        return lastIndexOf(array, target, 0, array.length);
    }

    // TODO: consider making this public
    private static int lastIndexOf(float[] array, float target, int start,
            int end) {
        for (int i = end - 1; i >= start; i--) {
            if (array[i] == target) {
                return i;
            }
        }
        return -1;
    }

    /**
     * Returns the least value present in {@code array}, using the same rules of
     * comparison as {@link Math#min(float, float)}.
     * 
     * @param array
     *            a <i>nonempty</i> array of {@code float} values
     * @return the value present in {@code array} that is less than or equal to
     *         every other value in the array
     * @throws IllegalArgumentException
     *             if {@code array} is empty
     */
    public static float min(float... array) {
        checkArgument(array.length > 0);
        float min = array[0];
        for (int i = 1; i < array.length; i++) {
            min = Math.min(min, array[i]);
        }
        return min;
    }

    /**
     * Returns the greatest value present in {@code array}, using the same rules
     * of comparison as {@link Math#min(float, float)}.
     * 
     * @param array
     *            a <i>nonempty</i> array of {@code float} values
     * @return the value present in {@code array} that is greater than or equal
     *         to every other value in the array
     * @throws IllegalArgumentException
     *             if {@code array} is empty
     */
    public static float max(float... array) {
        checkArgument(array.length > 0);
        float max = array[0];
        for (int i = 1; i < array.length; i++) {
            max = Math.max(max, array[i]);
        }
        return max;
    }

    /**
     * Returns the values from each provided array combined into a single array.
     * For example, {@code concat(new float[] a, b}, new float[] {}, new float[]
     * {c}} returns the array {@code a, b, c} .
     * 
     * @param arrays
     *            zero or more {@code float} arrays
     * @return a single array containing all the values from the source arrays,
     *         in order
     */
    public static float[] concat(float[]... arrays) {
        int length = 0;
        for (float[] array : arrays) {
            length += array.length;
        }
        float[] result = new float[length];
        int pos = 0;
        for (float[] array : arrays) {
            System.arraycopy(array, 0, result, pos, array.length);
            pos += array.length;
        }
        return result;
    }

    /**
     * Returns an array containing the same values as {@code array}, but
     * guaranteed to be of a specified minimum length. If {@code array} already
     * has a length of at least {@code minLength}, it is returned directly.
     * Otherwise, a new array of size {@code minLength + padding} is returned,
     * containing the values of {@code array}, and zeroes in the remaining
     * places.
     * 
     * @param array
     *            the source array
     * @param minLength
     *            the minimum length the returned array must guarantee
     * @param padding
     *            an extra amount to "grow" the array by if growth is necessary
     * @throws IllegalArgumentException
     *             if {@code minLength} or {@code padding} is negative
     * @return an array containing the values of {@code array}, with guaranteed
     *         minimum length {@code minLength}
     */
    public static float[] ensureCapacity(float[] array, int minLength,
            int padding) {
        checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
        checkArgument(padding >= 0, "Invalid padding: %s", padding);
        return (array.length < minLength) ? copyOf(array, minLength + padding)
                : array;
    }

    // Arrays.copyOf() requires Java 6
    private static float[] copyOf(float[] original, int length) {
        float[] copy = new float[length];
        System.arraycopy(original, 0, copy, 0,
                Math.min(original.length, length));
        return copy;
    }

    /**
     * Returns a string containing the supplied {@code float} values, converted
     * to strings as specified by {@link Float#toString(float)}, and separated
     * by {@code separator}. For example, {@code join("-", 1.0f, 2.0f, 3.0f)}
     * returns the string {@code "1.0-2.0-3.0"}.
     * 
     * @param separator
     *            the text that should appear between consecutive values in the
     *            resulting string (but not at the start or end)
     * @param array
     *            an array of {@code float} values, possibly empty
     */
    public static String join(String separator, float... array) {
        checkNotNull(separator);
        if (array.length == 0) {
            return "";
        }

        // For pre-sizing a builder, just get the right order of magnitude
        StringBuilder builder = new StringBuilder(array.length * 12);
        builder.append(array[0]);
        for (int i = 1; i < array.length; i++) {
            builder.append(separator).append(array[i]);
        }
        return builder.toString();
    }

    /**
     * Returns a comparator that compares two {@code float} arrays
     * lexicographically. That is, it compares, using
     * {@link #compare(float, float)}), the first pair of values that follow any
     * common prefix, or when one array is a prefix of the other, treats the
     * shorter array as the lesser. For example,
     * {@code [] < [1.0f] < [1.0f, 2.0f]
     * < [2.0f]}.
     * 
     * <p>
     * The returned comparator is inconsistent with
     * {@link Object#equals(Object)} (since arrays support only identity
     * equality), but it is consistent with
     * {@link Arrays#equals(float[], float[])}.
     * 
     * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
     *      Lexicographical order</a> article at Wikipedia
     * @since 2010.01.04 <b>tentative</b>
     */
    public static Comparator<float[]> lexicographicalComparator() {
        return LexicographicalComparator.INSTANCE;
    }

    private enum LexicographicalComparator implements Comparator<float[]> {
        INSTANCE;

        public int compare(float[] left, float[] right) {
            int minLength = Math.min(left.length, right.length);
            for (int i = 0; i < minLength; i++) {
                int result = Floats.compare(left[i], right[i]);
                if (result != 0) {
                    return result;
                }
            }
            return left.length - right.length;
        }
    }

    /**
     * Copies a collection of {@code Float} instances into a new array of
     * primitive {@code float} values.
     * 
     * <p>
     * Elements are copied from the argument collection as if by
     * {@code collection.toArray()}. Calling this method is as thread-safe as
     * calling that method.
     * 
     * @param collection
     *            a collection of {@code Float} objects
     * @return an array containing the same values as {@code collection}, in the
     *         same order, converted to primitives
     * @throws NullPointerException
     *             if {@code collection} or any of its elements is null
     */
    public static float[] toArray(Collection<Float> collection) {
        if (collection instanceof FloatArrayAsList) {
            return ((FloatArrayAsList) collection).toFloatArray();
        }

        Object[] boxedArray = collection.toArray();
        int len = boxedArray.length;
        float[] array = new float[len];
        for (int i = 0; i < len; i++) {
            array[i] = (Float) boxedArray[i];
        }
        return array;
    }

    /**
     * Returns a fixed-size list backed by the specified array, similar to
     * {@link Arrays#asList(Object[])}. The list supports
     * {@link List#set(int, Object)}, but any attempt to set a value to
     * {@code null} will result in a {@link NullPointerException}.
     * 
     * <p>
     * The returned list maintains the values, but not the identities, of
     * {@code Float} objects written to or read from it. For example, whether
     * {@code list.get(0) == list.get(0)} is true for the returned list is
     * unspecified.
     * 
     * <p>
     * The returned list may have unexpected behavior if it contains {@code NaN}
     * , or if {@code NaN} is used as a parameter to any of its methods.
     * 
     * @param backingArray
     *            the array to back the list
     * @return a list view of the array
     */
    public static List<Float> asList(float... backingArray) {
        if (backingArray.length == 0) {
            return Collections.emptyList();
        }
        return new FloatArrayAsList(backingArray);
    }

    @GwtCompatible
    private static class FloatArrayAsList extends AbstractList<Float> implements
            RandomAccess, Serializable {
        final float[] array;
        final int start;
        final int end;

        FloatArrayAsList(float[] array) {
            this(array, 0, array.length);
        }

        FloatArrayAsList(float[] array, int start, int end) {
            this.array = array;
            this.start = start;
            this.end = end;
        }

        @Override
        public int size() {
            return end - start;
        }

        @Override
        public boolean isEmpty() {
            return false;
        }

        @Override
        public Float get(int index) {
            checkElementIndex(index, size());
            return array[start + index];
        }

        @Override
        public boolean contains(Object target) {
            // Overridden to prevent a ton of boxing
            return (target instanceof Float)
                    && Floats.indexOf(array, (Float) target, start, end) != -1;
        }

        @Override
        public int indexOf(Object target) {
            // Overridden to prevent a ton of boxing
            if (target instanceof Float) {
                int i = Floats.indexOf(array, (Float) target, start, end);
                if (i >= 0) {
                    return i - start;
                }
            }
            return -1;
        }

        @Override
        public int lastIndexOf(Object target) {
            // Overridden to prevent a ton of boxing
            if (target instanceof Float) {
                int i = Floats.lastIndexOf(array, (Float) target, start, end);
                if (i >= 0) {
                    return i - start;
                }
            }
            return -1;
        }

        @Override
        public Float set(int index, Float element) {
            checkElementIndex(index, size());
            float oldValue = array[start + index];
            array[start + index] = element;
            return oldValue;
        }

        /** In GWT, List and AbstractList do not have the subList method. */
        /* @Override */public List<Float> subList(int fromIndex, int toIndex) {
            int size = size();
            checkPositionIndexes(fromIndex, toIndex, size);
            if (fromIndex == toIndex) {
                return Collections.emptyList();
            }
            return new FloatArrayAsList(array, start + fromIndex, start
                    + toIndex);
        }

        @Override
        public boolean equals(Object object) {
            if (object == this) {
                return true;
            }
            if (object instanceof FloatArrayAsList) {
                FloatArrayAsList that = (FloatArrayAsList) object;
                int size = size();
                if (that.size() != size) {
                    return false;
                }
                for (int i = 0; i < size; i++) {
                    if (array[start + i] != that.array[that.start + i]) {
                        return false;
                    }
                }
                return true;
            }
            return super.equals(object);
        }

        @Override
        public int hashCode() {
            int result = 1;
            for (int i = start; i < end; i++) {
                result = 31 * result + Floats.hashCode(array[i]);
            }
            return result;
        }

        @Override
        public String toString() {
            StringBuilder builder = new StringBuilder(size() * 12);
            builder.append('[').append(array[start]);
            for (int i = start + 1; i < end; i++) {
                builder.append(", ").append(array[i]);
            }
            return builder.append(']').toString();
        }

        float[] toFloatArray() {
            // Arrays.copyOfRange() requires Java 6
            int size = size();
            float[] result = new float[size];
            System.arraycopy(array, start, result, 0, size);
            return result;
        }

        private static final long serialVersionUID = 0;
    }
}
